Power transmission mechanism and manipulator

ABSTRACT

A power transmission mechanism comprising: a flexible power transmission element; a pair of a drive pulley and a driven pulley on which the flexible power transmission element is wound, each the pulley having a pin-embedding hole formed to extend from the outer circumferential thereof toward the center thereof, and a slit elongated in the circumferential direction of the pulley to extend to opposite sides of the embedding hole and communicating with the embedding hole; and a pair of columnar or tapered anchor pins each having a path hole penetrating the anchor pin across the lengthwise direction thereof to receive the flexible power transmission element inserted therein, wherein each the anchor pin receiving the flexible power transmission element in the path hole thereof is embedded in the embedding hole of the associated pulley under pressure, and the flexible power transmission element is thereby held on the pulley.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priorityfrom prior Japanese Patent Application No. 2003-96446, filed on Mar. 31,2003, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a manipulator such as anoperation-aiding manipulator or a manipulator for repairing a narrowportion of an energy device or the like. Especially, the presentinvention is intended to provide a power transmission mechanism using awire and pulleys, which can be reduced in size and can be enhanced inreliability, rigidity and user-friendliness.

[0004] 2. Related Background Art

[0005] In conventional laparoscope-assisted surgery such as laparoscopiccholecystectomy, a laparoscope 161, forceps 171, 172, etc. are insertedinto an abdominal cavity through trocars 154 set in small incisions 151,152, 153 made in the abdomen of a patient 150. Then, an operator(normally a surgeon) 160 conducts operation while watching the imageacquired by the laparoscope on a monitor 162 as shown in FIG. 31. Sincethis type of operation does not need to open the abdomen, physicalburden on the patient is alleviated, and the time required for recoveryand discharge from the hospital after operation is greatly reduced.Therefore, its adaptation to wider fields of application is expected.

[0006] Under the background, the Inventors already proposed a medicalmanipulator combining a robot technique to conventional forceps (robotforceps) 1 as shown in FIG. 32 (Japanese Patent Laid-openJP-2000-350735A). This manipulator 1 includes a control command unit 20having an attitude control unit 23 and a treatment control unit 24; aconnector unit 30 having one end connected to the control command unit20; a work unit 10 connected to the other end of the connecting unit 30and having a treatment unit 14 and supports 15 and 16 supporting thetreatment unit 14 to allow them to change in attitude in at least twodegrees of freedom of motion; and a controller (not shown) fordelivering a control command from the attitude control unit 23 to thesupports to change the attitude of the treatment unit 14 and fordelivering a control command from the treatment control unit 24 to thetreatment unit 14 to activate it.

[0007] The Inventors also proposed a medical manipulator as shown inFIG. 33 as another arrangement and degrees of freedom suitable forsuture and ligature (Japanese Patent Laid-open JP-2002-102248A). Thismedical manipulator 1 includes a work section 10, a control command unit20, and a connector unit 30 having opposite ends connected to the workunit 10 and the control command unit 20 respectively. In the worksection 10, a support unit, having a first rotation axis 11 intersectingthe axial direction 31 of the connector unit 30 and a second axis 12intersecting the first rotation axis 11, and a treatment unit (gripper)14 for working on the target site of surgery are aligned along thesecond rotation axis 12. In other words, the work section 10 has ayawing-axis joint support 15 and a rolling-axis joint support 16 thatfunction to support the gripper 14 to allow them to change in attitudein two degrees of freedom of motion. The control command unit 20includes: an attitude control unit 23 having a third rotation axis 21intersecting the center-axial direction 31 of the connector unit 30 anda fourth rotation axis 22 intersecting the third rotation axis 21; and atreatment control unit 24 gripped and operated by an operator whosewrist will rotate approximately in parallel to the fourth rotation axis22. The gripping motion 13 of the treatment unit 14 for working on thetarget site of surgery is given by the gripping motion 25 of thetreatment control unit 24.

[0008] In comparison with a remote-control master/slave manipulator, therobot forceps conjoin the control unit (master) and the forceps end hand(slave) to combine both an advantage of conventional forceps, namelyenabling large and quick motions which will be effected more easily andreliably by the operator, and an advantage of a manipulator, namely,enabling minute works or controls from difficult angles. Since the robotforceps have joints for twists, rotations, and other motions, at theend, they can change the attitude of the hand freely, and make sutureand ligature from various directions easier, which have been difficultwith conventional forceps. The robot forceps can be used together withconventional surgical appliances, for example, by handling the robotforceps with the right hand and handling conventional forceps with theleft hand. Additionally, because of the simple and compact system, therobot forceps can be introduced at a low cost.

[0009] Furthermore, manipulators having this type of configuration aresuitable also for works at locations difficult for the operator to workdirectly at the very site, such as repair works of narrow portions ofenergy devices. It will be needless to say that the size (length,thickness, dimension, etc.) of the manipulator will be determineddepending upon the nature of the intended work and the region of thework. Therefore, the robot forceps are not limited to the medical use.

[0010] Surgery-assisting manipulators and manipulators for repairingnarrow portions in energy devices, etc. are required to be compact,lightweight, durable, easy to operate, precisely responsive to intendedworks and inexpensive. To meet these requirements, their powertransmission mechanisms must be compact, lightweight, reliable, durableand inexpensive. Especially in the manipulators of the configurationsshown in Japanese Patent Laid-open Publications JP2000-350735A andJP2002-102248A, because of the restriction by the unitary structure ofthe master and the slave, their shapes, sizes, arrangements of the powertransmission mechanisms largely affect how they are easy to operate.

[0011] In robot and electromechanical devices and apparatuses includingmanipulators, power transmission for transmitting the power of anactuator to an end effector (such as a hand or tool) generally relies onwires and pulleys. In case a motion range of many revolutions isrequired in a power transmission mechanism using a wire and pulleys, itis usual to wind the wire 52 on pulleys 50, 51 as shown in FIG. 22 totransmit power by frictional force. To obtain a large transmissiontorque, a large frictional force is required. For this purpose, the wiremay be wound on the pulleys over a larger angle or multiply, or thetensile force of the wire may be increased. In any of these cases,however, since the drive force basically relies on friction, a decreaseof the tensile force, which may occur upon expansion of the wire, causesslips between the wire and the pulleys, and this invites a decrease ofthe torque. To cope with this problem, a tension adjusting mechanism issometimes added. Therefore, it complicates the mechanism, and increasesthe size and the cost of the device. Furthermore, it invites a decreaseof the rigidity of the joints. Furthermore, to wind the wire multiply onthe pulleys, the pulleys must be wide enough to accommodate the multipleturns of the wire, and invite an increase of the device size. Usually,surgery-assisting manipulators and manipulators for repairing narrowportions of energy devices, by nature, do not have ample spaces formultiply winding a wire. On the other hand, to hold the wire on thepulleys, a fastening member 53A is usually used as shown in FIG. 23.However, in case the wire is multiply wound on the pulleys, the motionrange (rotation angle) is usually limited to less than 180 degreesbecause of interference between the fastening member and the wire. Thereare some methods of increasing the winding angle as disclosed in thepublication of Japanese Patent No. 2,519,749. However, the maximum angleis about 270 degrees, and it is difficult to enable rotation of 360degrees or more. As far as the rotation range of pulleys is limited, themotion range of the manipulator joint, i.e. the work range of the endeffector, remains narrow and will disturb the work by the operator.Thus, the manipulator largely degrades in fidelity to intended works andcontrollability. To assure an ample work region not disturbing theworks, the manipulator needs the largest possible number of rotation,but this is difficult with conventional power transmission mechanisms.

[0012] On the other hand, in the power transmission mechanism using awire and pulleys as shown in FIG. 24, in case the wire diameter is smallor the drive pulley and the driven pulley are apart by a long distance,influence of elastic deformation (expansion) of the wire may increaseand disable transmission of sufficient power. In addition, there is theproblem that sufficient rotational rigidity is not obtained at thedriven shaft (output shaft) in a hold mode where the drive pulley isstationary or in a servo lock mode. If the desired rotational rigidityis not obtained, then the manipulator degrades in controllability andfidelity to intended works, and operator cannot perform sufficientworks.

[0013] In the master-slave combined manipulator conjoining the masterand the slave as shown in FIGS. 25 and 27, eccentric mass about theconnector unit 30 is usually produced. Depending upon the location ofthe eccentric mass, rotational torque out of the operator's intentionmay be produced by the weight about the connector unit, which degradesthe controllability. Especially in the initial status at the start ofcontrols or in the basic attitude of the manipulator, which is the moststandard attitude for controls, if rotational torque is produced byeccentric mass about the connector unit, it will impose useless load tothe operator and may invite significant degradation of controllability.In addition, in the manipulator having the common rolling axis, pitchingaxis and rolling axis as shown in FIG. 25, it is difficult to change theattitude of the work section to the yawing direction (lateral orright-and-left direction) from the basic attitude illustrated because itis the change of attitude to the singular configuration. In thearrangement of degrees of freedom shown in FIG. 29, having theillustrated common rolling axis, yawing axis, rolling axis, it isdifficult to change the attitude of the work section from theillustrated basic attitude to the pitching direction (vertical orup-and-down direction) because it is the change of attitude to thesingular configuration. In actual controls of the manipulator, theattitude of the work section is changed more frequently to the lateraland vertical directions from the basic attitude. Therefore, thearrangement for degrees of freedom of motion shown in FIG. 25 or 29 willinvite degradation of controllability.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of the invention to reduce the size andenhance the reliability, rigidity and controllability of various kindsof manipulators.

[0015] According to an embodiment of the invention, there is provided apower transmission mechanism comprising: a flexible power transmissionelement; a pair of a drive pulley and a driven pulley on which theflexible power transmission element is wound, each said pulley having apin-embedding hole formed to extend from the outer circumferentialthereof toward the center thereof, and a slit elongated in thecircumferential direction of the pulley to extend to opposite sides ofthe embedding hole and communicating with the embedding hole; and a pairof columnar or tapered anchor pins each holding the flexible powertransmission element on the pair of pulleys, each said anchor pin havinga path hole penetrating the anchor pin across the lengthwise directionthereof to receive the flexible power transmission element insertedtherein, wherein each said anchor pin receiving the flexible powertransmission element in the path hole thereof is embedded in theembedding hole of the associated pulley under pressure, and the flexiblepower transmission element is thereby held on the pulley.

[0016] According to another embodiment of the invention, there isprovided a power transmission mechanism comprising: a flexible powertransmission element; and a pair of a drive pulley and a driven pulleyon which the flexible power transmission element is wound, wherein atleast one of two spans of the flexible power transmission elementspanning between the pair of pulleys is covered by a hollow elongatemember, or cut and connected by a solid elongate member.

[0017] According to still another embodiment of the invention, there isprovided a manipulator having a work unit, connector unit and a controlunit to activate the work unit under a control command given from thecontrol unit to the work unit through the connector unit, comprising: apower transmission mechanism for transmitting a control command from thecontrol unit to the work unit; and a driving device for driving thepower transmission mechanism, and having an eccentric mass about theconnector unit, wherein the power transmission mechanism includes aflexible power transmission element, and a pair of a drive pulley and adriven pulley on which the flexible power transmission element is wound,and wherein the drive pulley and the driven pulley are oriented to makea twist between the rotation axes thereof to position the center ofgravity of the driving device as the eccentric mass about the connectorunit in a vertically lower area of the connector unit when themanipulator takes the basic attitude thereof.

[0018] According to the invention, the power transmission mechanismusing a wire (flexible power transmission element) and pulleys requiresno tension adjusting mechanism required in conventional frictional drivesystems, and has the structure in which the wire does not interfere withthe portion for firmly holding the wire on the pulleys. Therefore, thepower transmission mechanism meets the requirements of space saving andmultiple rotations. Further, the fastening force is enhanced by thewedge effect. Accordingly, the motion region of the manipulatorjunction, i.e. the work area of the end effector, is wide enough toallow smooth works. Therefore, the manipulator is greatly improved infidelity to intended works and in controllability.

[0019] In addition, since at least one of two spans of the wire (thespan of the wire subjected to higher tensile force) between the drivepulley and the driven pulley is covered by a hollow elongate member orconnected by a solid elongate member, influence of elastic deformation(expansion) of the wire is small enough to assure transmission ofsufficient power even when the wire is thin, or the drive pulley and thedriven pulley are apart by a long distance. Further, in a hold modewhere the drive pulley is stationary or in a servo lock mode, sufficientrotational rigidity is obtained at the driven shaft (output shaft).Therefore, reliable power transmission is assured, and the manipulatoris greatly improved in fidelity to intended works and incontrollability.

[0020] Moreover, since the manipulator has the configuration free fromrotational torque caused by eccentric mass about the connector unit inthe basic attitude of the manipulator, which is the most standardattitude in the initial status at the start of controls or duringcontrols, the manipulator is enhanced in fidelity to intended works andin controllability without compelling the operator to exert uselesscontrol force. Furthermore, the degrees of freedom of motion have thecommon rolling axis by the connector unit, bent axis in the aslantdirection between the yawing axis (lateral direction) and the pitchingaxis (vertical direction), and rolling axis. Therefore, it is easy tochange the attitude of the work section from the basic attitude, and themanipulator is significantly improved in fidelity to intended works andin controllability.

[0021] That is, it is possible to provide a power transmission mechanismthat is compact, lightweight, reliable, rigid and inexpensive, and byincorporating the power transmission mechanism, it is possible toprovide a manipulator for assisting surgery or repairing narrow portionin energy devices, which is enhanced in controllability and in fidelityto intended works.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a set of a front elevation of a power transmissionmechanism according to the first embodiment of the invention, its rightand left side elevations, and its sectional views taken along the d-dline and e-e line;

[0023]FIG. 2 is a schematic exploded perspective view showing theentirety of the power transmission system according to the firstembodiment of the invention;

[0024]FIG. 3 is a schematic perspective view of a manipulatorincorporating the power transmission mechanism according to the firstembodiment of the invention;

[0025]FIG. 4 is a perspective view of a pulley used in the powertransmission mechanism according to the first embodiment of theinvention;

[0026]FIG. 5 is a perspective view of an anchor pin used in the powertransmission mechanism according to the first embodiment of theinvention;

[0027]FIG. 6 is a set of diagrams showing an assembling procedure of thepower transmission mechanism according to the first embodiment of theinvention;

[0028]FIG. 7 is a set of diagrams showing various shapes of the anchorpin used in the power transmission mechanism according to the firstembodiment of the invention;

[0029]FIG. 8 is a front elevation of a power transmission mechanismaccording to the second embodiment of the invention;

[0030]FIG. 9 is a front elevation of another type of power transmissionmechanism according to the second embodiment of the invention;

[0031]FIG. 10 is a front elevation of another type of power transmissionmechanism according to the second embodiment of the invention;

[0032]FIG. 11 is a front elevation of another type of power transmissionmechanism according to the second embodiment of the invention;

[0033]FIG. 12 is a front elevation of another type of power transmissionmechanism according to the second embodiment of the invention;

[0034]FIG. 13 is a front elevation of a support member used in the powertransmission mechanism according to the second embodiment of theinvention;

[0035]FIG. 14 is a transverse sectional view of the support member setin a pipe of the power transmission mechanism according to the secondembodiment of the invention;

[0036]FIG. 15 is a perspective view of a manipulator according to thethird embodiment of the invention;

[0037]FIG. 16 is a perspective view of the manipulator according to thethird embodiment of the invention, which illustrates a relation betweena wire and pulleys;

[0038]FIG. 17 is a perspective view of the manipulator according to thethird embodiment;

[0039]FIG. 18 is a perspective view of the manipulator according to thethird embodiment of the invention, which illustrates a relation betweenthe wire and pulleys;

[0040]FIG. 19 is a perspective view of the manipulator according to thethird embodiment of the invention;

[0041]FIG. 20 is a perspective view of the manipulator according to thethird embodiment of the invention, which illustrates a relation betweenthe wire and pulleys;

[0042]FIG. 21 is a diagram showing a posture of an operator;

[0043]FIG. 22 is a set of a front elevation of a conventional powertransmission mechanism, its right and left side elevations, and verticalsectional views taken along the d-d line and the e-e line;

[0044]FIG. 23 is a set of a front elevation of a conventional powertransmission mechanism, its right and left side elevations, andsectional views;

[0045]FIG. 24 is a front elevation of the conventional powertransmission mechanism;

[0046]FIG. 25 is a perspective view of a conventional manipulator;

[0047]FIG. 26 is a perspective view of the conventional manipulator,which illustrates a relation between a wire and pulleys;

[0048]FIG. 27 is a perspective view of a conventional manipulator;

[0049]FIG. 28 is a perspective view of the conventional manipulator,which illustrates a relation between a wire and pulleys;

[0050]FIG. 29 is a perspective view of a conventional manipulator;

[0051]FIG. 30 is a perspective view of the conventional manipulator,which illustrates a relation between a wire and pulleys;

[0052]FIG. 31 is a diagram for explaining surgery under a laparoscope;

[0053]FIG. 32 is a perspective view of a conventional manipulator; and

[0054]FIG. 33 is a perspective view of a conventional manipulator.

DETAILED DESCRIPTION OF THE INVENTION

[0055] Explained below are some embodiments of the invention withreference to the drawings.

[0056]FIG. 1 is a set of sectional views and side elevations showing thedriving and driven wire/pulley portions in a power transmissionmechanism according to the first embodiment of the invention. FIG. 2 isa schematic diagram of the entire power transmission system, with itscomponents being exploded. FIG. 3 is a schematic diagram showing amanipulator incorporating the same power transmission mechanism. Asshown in FIG. 1, the power transmission mechanism of a manipulatoraccording to the first embodiment of the invention includes a drivepulley 50, driven pulley 51, wire (flexible power transmission element)52, columnar or tapered pin 53, and wire connecting member (not shown).The wire is usually a stainless wire rope, but a rope of any othermaterial such as tungsten or fabric materials are usable withoutproblems, provided it is elastic. In the present invention, the wirecontemplates any of all these materials. The wire connecting member isan element necessary for connecting opposite ends of one linear wire tomake a loop.

[0057] The wire 52 is loop-shaped, and it is wound on pulleys 50 51 by1.5 turns respectively in this first embodiment. The wire 52 is firmlyheld on the pulleys 50, 51 by anchor pins 53 (fastening portions). Inthis configuration, the maximum motion range of ±270 degrees isobtained.

[0058]FIG. 2 shows an example of the entire power transmission system inwhich a motor 54 with a reducer is associated with the drive pulley 50whereas an arm 55 is associated with the driven pulley 51. However, thesystem is not limited to this configuration. Basically, the system is apower transmission mechanism for transmitting power from the drive sideto the driven side. Similarly, although FIG. 3 shows an example ofincorporating the system in a manipulator 1, combination of the systemand the manipulator 1 is not limited to this configuration. Themanipulator 1 is composed of a work unit 10, control unit 20, connectorunit 30, control unit (not shown), and others, and the operator adjuststhe position and attitude of the work unit by controlling thecontroller. This manipulator is used for works in narrow portions orinserted through a narrow portion to work. Therefore, the work unit 10must be compact. Additionally, for enhanced fidelity to intended worksand operability, a sufficient motion region (rotation angle of thedriven shaft) is required.

[0059] To illustrate details of the drive unit, FIG. 4 shows aperspective view of the pulley 50 or 51. Basically, the drive pulley 50and the driven pulley 51 may be identical in structure. The pulley 50has a slit 56 wide enough to receiving the wire and a columnar ortapered hole (embedding hole) 57 at a central position thereof. The hole57 is formed to extend from the outer circumferential surface of thepulley 50, 51 toward its center, and the slit 56 communicates with thehole 57. FIG. 5 shows a perspective view of the anchor pin 53 for firmlyholding the wire 12 on the pulley 50. The slit 56 is formed to extendlaterally, i.e. in parallel with the tangential line of thecircumferential surface of the pulley 50, 51. The anchor pin 53 has acolumnar or tapered shape, and has a hole 58 extending across the anchorpin 53 and large enough to pass the wire approximately at its center.FIG. 6 is a set of diagrams (a) through (c) illustrating procedures foranchoring the anchor pin 53. After the wire is inserted through the hole58 in its central location of the columnar or tapered anchor pin 53, thecolumnar or tapered anchor pin 53 is inserted in the columnar or taperedhole 57 of the pulley 50. Thus, the wire 52 is reliably held on thepulley 50. That is, the diameter of the anchor pin 53 is larger than theinner diameter of the hole 57 to be firmly held in the hole 57 bycompression engagement. The anchor pin 53 is sized and shaped so thatthe top surface thereof becomes flush with the outer circumferentialsurface of the pulley 50. In this manner, even when the rotation angleis large, one turn of the wire does not interfere the other turns of thewire. Further, tapering one or both of the hole 57 and the anchor pin 53assures firmer engagement of the wire 52 with the pulley 50 by a wedgeeffect. Therefore, it is possible to hold the wire 52 on the pulley 50more firmly, multiple winding is also possible.

[0060]FIG. 7 is a set of diagrams showing various shapes of the hole 8that can be made in the tapered or columnar anchor pin 53. The anchorpin 53 is made of an elastic material, and reduces its diameter whencompressed. The circular hole 58 shown at (a) can be made at a low cost.When the hole 58 includes a slit 58 a for contraction of the anchor pin53 as shown at (b) through (d) in FIG. 7, the hole 58 easily deforms andcan efficiently transmit the compression force by the wedge effect.Therefore, the compression force further increases.

[0061] Moreover, in the instant embodiment of the invention, theassembly of the wire 52 to the pin 53 and the assembly of the pin 53 tothe pulley 50 can be done simultaneously by inserting the pin 53 in tothe tapered hole 57. Therefore, the labor effectiveness of the assemblyis improved.

[0062] According to the first embodiment, since the power transmissionmechanism using the wire 52 and the pulleys 50 551 needs no specialmechanism for adjustment of the tensile force required in conventionalfrictional drive systems; different turns of the wire 52 do notinterfere at the hold portions on the pulleys 50, 51; and the wedgeeffect exerts a strong fastening power. Therefore, wider extension isassured as the motion region of the manipulator's joint, namely, thework region of the end effector, which is large enough to assure smoothworks with the manipulator. Thus, the manipulator is greatly enhanced infidelity to intended works and in controllability.

[0063]FIGS. 8 through 12 are simplified sectional views of thewire/pulley portions at the drive side and the lower side in a powertransmission mechanism of a manipulator according to the secondembodiment of the invention. Here are shown examples of the use of ahollow tube (as a hollow elongate member, also in the description hereinbelow) covering one or both of the spans of the wire 52 between thepulleys 50 and 51, or the use of a solid cord (or a solid rod, as asolid elongate member, also in the description herein below) connectingone or both of the spans of the wire 52 between the pulleys 50 and 51.As shown n these figures, there are various possible ways of connectingthe wire 52 to the pulleys, and any of them is employable withoutproblems. In the examples shown in FIG. 9 and FIG. 11, the wire 52 neednot pass through the lower hollow tube 60 a, but it may be secured tothe hollow tube 60 a at two or more different points. Since the pullstrength of the portions of fixture is usually lower than the pullstrength of the wire 52 itself, it is important to assure the reliablestrength at the points of fixture. However, when the wire 52 is insertedall through the hollow tube 60 a, the pull strength at least of the wire52 is ensured. Therefore, breakage of the points of fixture by defectivefixture (for example, fixture by pressure) can be prevented.

[0064] In FIGS. 8 through 11, at least one of two spans of the wire 52subjected to higher tensile force (lower span of the wire) is connectedby the solid cord 60 b, or inserted in the hollow tube 60 a. That is,one of two spans of the wire 52 (power transmission system) spanningbetween the pair of pulleys 50, 51, which is subjected to a highertensile force, is reinforced by the hollow tube 60 a or the solid cord60 b. As such, in case one of two spans of the wire 52 is subjected tohigher tensile force (assume it be the lower span of the wire),sufficient effect will be obtained by inserting at least the span of thewire 52 subjected to higher tensile force through the hollow tube 60 aor connecting it with the solid cord 60 b.

[0065]FIG. 12 shows an example in which the hollow tube 60 a, or thesolid cord 60 b, is supported in holes 61 a, 61 of disk-shaped supportmembers 61. In FIG. 12, each support member 61 has six holes 61 a, 61,and two of them are used to insert and support the hollow tube 60 a, orthe solid cord 60 b. The number of holes is determined by the number ofdrive axes.

[0066] In the case where both spans of the wire 52 (upper and lowerspans in the figure) are inserted in the hollow tubes 60 a, or connectedby the solid cords 60 b, as far as the shafts of the drive pulley 50 andthe driven pulley 51 are oriented perpendicularly, the upper and lowerspans of the wire 52 having the hollow tubes 60 a or the solid cords 60b are well balanced in gravity. Therefore, the gravity components of thehollow tube 60 a or the solid cord 60 b do not increase the drivetorque. However, if both spans of the wire 52 lie to align on the samehorizontal level, gravity of the hollow tube 60 a or the solid cord 60 bmay exert non-negligible influences to the tensile force of the wire 52.In an extreme case, it invites an increase of the vibration or breakageof the wire. To cope with this problem, the use of the support members61 to support the hollow tube 60 a or solid cord 60 b as shown in FIG.12 contributes to reducing the influences of the gravity. In case thedrive pulley 50 are formed in a pipe 62 as a part of the connector unit30, the support members 61 as shown in FIG. 13 may be located and fixedat some positions in predetermined intervals inside the pipe 62 as shownin FIG. 14.

[0067] According to the second embodiment, since the at least one of twospans of the wire between the drive pulley 50 and the driven pulley 51,which is subjected to higher tensile force, is inserted in the hollowtube 60 a or connected by the solid cord 61 b, even when the wire 52 isthin, or the drive pulley 50 and the driven pulley 51 are apart by a logdistance, it is possible to reduce the influence of the elasticdeformation (expansion) of the wire 52 during transmission of power muchenough to ensure transmission of sufficient power, and it is possible toobtain sufficient rotational rigidity at the driven shaft (output shaft)in the hold mode where the drive pulley is stationary or in the servolock mode. Additionally, the support members can prevent unacceptableincrease of vibration caused by the gravity of the hollow tube or solidrod and breakage of the wire. Therefore, the power transmissionmechanism ensures reliable power transmission, and the manipulator isgreatly enhanced in fidelity to intended works and in controllability.

[0068]FIGS. 15 through 20 are perspective views of manipulatorsaccording to the third embodiment of the invention and diagrams showingtheir wire/pulley portions. In the master-slave combined manipulatorconjoining the master and the slave, the center of gravity of thedriving device is remote from the connector unit 30. Therefore,eccentric mass about the connector unit 30 is produced in most cases.Depending upon the position of the eccentric mass, rotational torque outof the operator's intention may be produced about the connector unit 30by influences of the gravity, and this may invite degradation of thecontrollability. Especially in the initial status at the start ofcontrols of the manipulator or in the basic attitude of the manipulator,which is the most standard attitude for controls, if rotational torqueis produced by eccentric mass about the connector unit, it will imposeuseless load to the operator and may invite significant degradation ofcontrollability.

[0069] In most cases, it is the drive motor 54 that has the massoccupying a great part. Tanking it into consideration, the manipulatorsshown in FIGS. 15 through 20 are configured to locate the center ofgravity of the drive motor 54 below the connector unit 30 when themanipulator takes the basis attitude. That is, orientation of the drivepulley 50 is twisted with respect to the orientation of the drivenpulley 51 in comparison with, for example, FIG. 6. Although the optimumbasic attitude of the manipulator varies depending upon the work to beeffected, FIG. 15 shows the degrees of freedom of motion including thecommon rolling axis (about the axis of the connector unit 30), pitchingaxis and the rolling axis. Although the conventional system locates themotors 54 to lie in the horizontal direction as shown in FIG. 25 in thebasic attitude of the manipulator, and it invites degradation ofcontrollability because of bad balance of weights. The instantembodiment, however, orients the drive pulley 50 and the driven pulley51 with the twist of 90 degrees relative to each other so that thecenter of gravity of each motor 54 comes downward when the manipulatortakes the basis attitude. Therefore, the manipulator is well balanced inweight, and therefore excellent in controllability. FIG. 16 shows arelation between the wire 52 and the pulleys 50, 51. The manipulatorshown in FIG. 17 has the degrees of freedom of motion including thecommon rolling axis, pitching axis and yawing axis. However, here again,it has the twist of 90 degrees between the pulleys 50, 51 as shown inFIG. 18. Combination of components for giving such a twist is notlimited to the combination of the drive pulley 50 and the driven pulley51, but the twist may be given between an interposed idle pulley 51 aand the pulley 50 (or 51) as shown in the same FIG. 18.

[0070] The manipulator shown in FIG. 19 has the degrees of freedom ofmotion including the common rolling axis, pitching axis of yawing axis,and rolling axis. Here again, the twist of approximately 45 degrees isgiven between the drive pulley 50 and the driven pulley 51. In thiscase, the rotation axis 63 of the work unit 10 and the rotation axis 64of the control unit 20 coincide approximately. In the arrangement anddegrees of freedom shown in FIG. 15 having the common rolling axis,pitching axis and rolling axis, it is difficult to change the attitudeof the work unit 10 to the yawing direction (lateral direction) from theillustrated basic attitude because of the singular configuration. In thearrangement and degrees of freedom of motion shown in FIG. 29 having thecommon rolling axis, yawing axis and rolling axis, it is difficult tochange the attitude of the work unit to the pitching direction (verticaldirection) because of the singular configuration. In actual controls ofthe manipulator, it is most often to change the attitude of the workunit from the basic attitude to the lateral and vertical directions, andthe arrangements for degrees of freedom shown in FIGS. 25 and 29 invitedegradation of controllability.

[0071] In laparoscopic surgery, the operator 160 takes the posture shownin FIG. 21 during operation. Therefore, the most natural orientations ofthe operator's hands are approximately 45 degrees inward respectively.Therefore, the embodiment shown in FIG. 19 having the arrangement ofdegrees of freedom including the common rolling axis, intermediatedirection between the pitching axis and the yawing axis (aslant by 45degrees approximately) and rolling axis, it is possible to coincide theeasiest orientation to control the manipulator with the most naturalorientation of a hand of the operator, and simultaneously, the motor 54having a heavy mass can be placed to orient downward. Therefore, thismanipulator minimizes the fatigue of the operator, and itscontrollability is significantly enhanced. Relative inclination betweenthe two pulleys 50, 51 need not be 45 degrees. Instead, only when it isoffset from the pitching axis direction and yawing axis direction evenby a slight amount, controllability of the manipulator is improvedbecause the up-and-down direction and the right-and-left direction areoffset from the singular configuration.

[0072] Furthermore, it is also possible to employ a structure capable offreely giving a desired twisting degree between the drive axis pulleyand the driven axis pulley such that the motor comes in a lower areawhen the manipulator takes the basic attitude optimum for the intendedwork.

[0073] According to the invention, the power transmission mechanismusing a wire and pulleys needs no special mechanism for adjusting thetensile force required in conventional frictional drive systems, and hasthe structure in which the wire does not interfere with the portion forfirmly holding the wire on the pulleys. Therefore, the powertransmission mechanism meets the requirements of space saving andmultiple rotations. Further, the fastening force is enhanced by thewedge effect. Accordingly, the motion region of the manipulatorjunction, i.e. the work area of the end effector, is wide enough toallow smooth works. Therefore, the manipulator is greatly improved infidelity to intended works and in controllability.

[0074] In addition, since at least one of two spans of the wire (thespan of the wire subjected to higher tensile force) between the drivepulley and the driven pulley is covered by a hollow tube or connected bya solid cord, influence of elastic deformation (expansion) of the wireis small enough to assure transmission of sufficient power even when thewire is thin, or the drive pulley and the driven pulley are apart by along distance. Further, in the hold mode where the drive pulley isstationary or in a servo lock mode, sufficient rotational rigidity isobtained at the driven shaft (output shaft). Therefore, reliable powertransmission is assured, and the manipulator is greatly improved infidelity to intended works and in controllability.

[0075] Moreover, since the manipulator has the configuration free fromrotational torque caused by eccentric mass about the connector unit inthe basic attitude of the manipulator, which is the most standardattitude in the initial status at the start of controls or duringcontrols, the manipulator is enhanced in fidelity to intended works andin controllability without compelling the operator to exert uselesscontrol force. Furthermore, the degrees of freedom of motion have thecommon rolling axis by the connector unit, bent axis in the aslantdirection between the yawing axis (lateral direction) and the pitchingaxis (vertical direction), and rolling axis. Therefore, it is easy tochange the attitude of the work section from the basic attitude, and themanipulator is significantly improved in fidelity to intended works andin controllability.

[0076] That is, it is possible to provide a power transmission mechanismthat is compact, lightweight, reliable, rigid and inexpensive, and byincorporating the power transmission mechanism, it is possible toprovide a manipulator for assisting surgery or repairing narrow portionin energy devices, which is enhanced in controllability and in fidelityto intended works.

[0077] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concepts as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A power transmission mechanism comprising: aflexible power transmission element; a pair of a drive pulley and adriven pulley on which the flexible power transmission element is wound,each said pulley having a pin-embedding hole formed to extend from theouter circumferential thereof toward the center thereof, and a slitelongated in the circumferential direction of the pulley to extend toopposite sides of the embedding hole and communicating with theembedding hole; and a pair of columnar or tapered anchor pins eachhaving a path hole penetrating the anchor pin across the lengthwisedirection thereof to receive the flexible power transmission elementinserted therein, wherein each said anchor pin receiving the flexiblepower transmission element in the path hole thereof is embedded in theembedding hole of the associated pulley under pressure, and the flexiblepower transmission element is thereby held on the pulley.
 2. The powertransmission mechanism according to claim 1 wherein the anchor pin ismade of an elastic material and reduces its diameter when compressed. 3.The power transmission mechanism according to claim 1 wherein the outerdiameter of the anchor pin is larger than the inner diameter of theembedding hole of the pulley.
 4. The power transmission mechanismaccording to claim 1 wherein the slit of the pulley extendssubstantially parallel with a tangential line of a point on the outercircumferential surface of the pulley.
 5. The power transmissionmechanism according to claim 1 wherein the path hole of the anchor pinincludes a slit portion extended along the axial direction of the anchorpin to permit the path hole to reduce the diameter thereof when insertedin the embedding hole under pressure.
 6. The power transmissionmechanism according to claim 5 wherein the slit portion of the path holein each said anchor pin extend to one or both of the upward directionand the downward direction along the axial direction of the anchor pin.7. The power transmission mechanism according to claim 6 wherein theslit portion extends upward along the axial direction of the anchor pinand penetrates the top surface of the anchor pin to divide it.
 8. Apower transmission mechanism comprising: a flexible power transmissionelement; and a pair of a drive pulley and a driven pulley on which theflexible power transmission element is wound, wherein at least one oftwo spans of the flexible power transmission element spanning betweenthe pair of pulleys is covered by a hollow elongate member, or cut andconnected by a solid elongate member.
 9. The power transmissionmechanism according to claim 8 wherein both of the two spans of theflexible power transmission element are cut and connected by solidelongate members.
 10. The power transmission mechanism according toclaim 8 wherein one of the two spans of the flexible power transmissionelement is cut and connected by a solid elongate member, and the otheris covered by a hollow elongate member.
 11. The power transmissionmechanism according to claim 8 wherein the hollow elongate member issecured to the flexible power transmission element passing therein at aplurality of positions.
 12. The power transmission mechanism accordingto claim 8 further comprising a support member permitting the hollowelongate member or the solid elongate member to pass slidablytherethrough to support the same.
 13. The power transmission mechanismaccording to claim 12 wherein a plurality of said support members areprovided between the pair of pulleys.
 14. The power transmissionmechanism according to claim 12 wherein the support member is adisk-shaped member having a plurality of holes capable of receiving thehollow elongate member or the solid elongate member slidably.
 15. Thepower transmission mechanism according to claim 12 wherein the supportmember is secured inside a pipe-shaped member.
 16. A manipulator havinga work unit, connector unit and a control unit to activate the work unitunder a control command given from the control unit to the work unitthrough the connector unit, comprising: a power transmission mechanismfor transmitting a control command from the control unit to the workunit; and a driving device for driving the power transmission mechanism,and having an eccentric mass about the connector unit, wherein the powertransmission mechanism includes a flexible power transmission element,and a pair of a drive pulley and a driven pulley on which the flexiblepower transmission element is wound, and wherein the drive pulley andthe driven pulley are oriented to make a twist between the rotation axesthereof to position the center of gravity of the driving device as theeccentric mass about the connector unit in a vertically lower area ofthe connector unit when the manipulator takes the basic attitudethereof.
 17. The manipulator according to claim 16 wherein thearrangement for degrees of freedom of motion includes a common rollingaxis by the connector unit, a bent axis permitting rotation in anintermediate aslant direction between the yawing axis for permittingrotation in the lateral direction and the pitching axis permittingvertical rotation, and a rolling axis.
 18. The manipulator according toclaim 16 wherein the twist angle between the rotation axis of the drivepulley and the rotation axis of the driven pulley is adjustable.
 19. Themanipulator according to claim 16 wherein the driving device includes adrive motor for driving the power transmission mechanism, and the centerof gravity of the drive motor about the connector unit is located belowthe connector unit.
 20. The manipulator according to claim 16 whereinthe twist angle between the rotation axis of the driven pulley and therotation axis of the drive pulley is approximately 45 degrees.